The claimed invention is related to analytical instrumentation, in particular, to spectroscopy, spectroscopic methods and devices for measurement of spectroscopic properties of loose products based on replenishment of a portion of the measured sample in the measurement zone and can be used for qualitative and quantitative analysis, for example, analysis of properties of the whole grain.
Methods of infrared spectroscopy has applications in industry and agriculture, they allow to perform fast testing of product'properties on different stages of production, during transportation and storage. For example, it is a commonly accepted practice to make spectroscopic analysis of grain to determine its properties and constituents such as moisture, protein content etc. immediately after harvesting, before loading grain into a storage silo, after transportation and prior to be used for sowing or for baking.
The main requirements to the results of spectroscopic analysis are their reliability and reproducibility. A particular feature of analysis of loose products is an optical inhomogeneity of the samples by its nature, so during analysis several areas of sample or several portions of the same sample have to be measured and then averaged. Therefore it is crucial for obtaining reliable and reproducible results to have constant and reproducible filling of the measurement zone with loose product from sample to sample.
It is known that there is a method of measurement of spectroscopic properties of loose samples [1, 2], that comprises manual filling of the optical cell with a loose product, placing the cell in the measurement zone, measurement of spectroscopic properties of the product in several areas of the filled cell, the cell being immobile during the measurement and being moved between the measurements using a special scanning device. Scanning may be done either by linear movement [1] or by rotation [2] of the optical cell.
The main shortcoming of this method is a necessity to fill the cell manually, that decreases reproducibility of the filling and the speed of analysis, and also increases cost. It becomes important in case if it is necessary to make express analysis of large amounts of product, for example before loading grain into the storage silo during harvesting. Moreover, results of analysis depend upon how accurately the cell was filled (i.e. on qualification of the operator).
It is known that there'a device for measurement of spectroscopic properties of loose products [1], that comprises an optical cell, a device for movement of the optical cell and a measuring device.
But the known device does not have any means for automatic loading and discharge of the measured sample. A set of cell with fixed path lengths that can't be readjusted is used.
It is known that there is a method and there is a device for measurement of spectroscopic properties of loose products [3]. This method comprises delivery of product in the measurement zone under influence of gravity, stopping the sample in the measurement zone with a shutter placed below the measurement zone, compacting the product by vibration, measurement of spectroscopic properties of the sample in still position and discharge of the sample by opening the shutter.
The device for implementation of this known method includes a channel (pipeline) in which the loose product moves, a measurement zone in which the loose flow has a component along the gravity force, a measuring optical window, an optical unit for spectroscopic measurements, a valve (shutter) placed below the measuring optical window that locks the measurement zone to keep the product in the zone, branch of the additional channel (bypass), located upper than the measurement zone that provides the constant level of the product in the measurement zone and the product flow through the main channel (pipeline), and a drive that produces vibration to make sample dense.
This method and the device for its implementation provide automatic loading and discharge of a sample. Constant and reproducible density of the product in the measurement zone is achieved by the constant level of the product and by compacting the sample before measurement to make it dense by shaking.
The main shortcoming of this method of measurement of spectroscopic properties of the loose samples and the device for its implementation is that the vibrations that are used to create dense product in the measurement zone could lead to disadjustment of the optical unit of the device, that in turn would lead to less reliable and reproducible results of measurements, while various methods for protection of the optical unit from vibration increase the complexity and costs of the device drastically.
The method and the device described in [4] are the closest to the claimed invention by the combination of the essential parameters. The method comprises delivery of the sample to the measurement zone using a device for portioned sampling, that loads a certain amount of portions of the product; the measurement zone implemented as a vertical shaft that is closed in the bottom part during the sample loading and the measurement by a special locking device, then the registration of the spectroscopic properties of the sample in a still position. In this way the sample is in motion or still during the measurement, but the measurement of the spectroscopic properties is made when the sample is still.
The device for implementation of this known method of measurement of spectroscopic properties includes a loading bunker, portioned sampling unit made as a paddle wheel, vertical shaft, spectral properties measurement unit, a locking unit that closes the vertical shaft periodically, and a discharge bunker.
This method and the device for its implementation ensure automatic loading and discharge of the sample, that increase the speed of analysis and guarantees that the results are independent form the qualification of the operator.
But the present method and the device do not provide the constant bulk density of the product in the measurement zone with desired accuracy. The device does not provide means for strict control of the volume of the sample loaded in the measurement zone and significant inhomogeneities of the product bulk density in the measurement zone might be caused, for example, by the sample sticking to the paddles of the loading wheel that is quite probable when the products with high moisture content are measured. Moreover, the possibility to adjust the length of the optical path depending on the spectroscopic properties of the product analysed is missing, that decreases the accuracy and reproducibility of the analysis.